Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
J Chem Phys. 2011 Feb 14;134(6):064109. doi: 10.1063/1.3548889.
Crystallization is fundamental to many aspects of physics and chemistry in addition to being of technological relevance, for example, in the chemical, food, and pharmaceutical industries. However, the design of crystalline materials and crystallization processes is often challenging due to the many variables that can influence the process. As a part of an effort to gain a molecular-level understanding of the way molecules aggregate and organize themselves into crystal structures, in this work we present a new method to construct order parameters suitable for the study of crystallization and polymorph transformations in molecular systems. Our order parameters can be systematically defined for complex systems using information that can be obtained from simple molecular dynamics simulations of the crystals. We show how to construct the order parameters for the study of three different systems: the formation of α-glycine crystals in solution, the crystallization of benzene from the melt, and the polymorph transformation of terephthalic acid. Finally, we suggest how these order parameters could be used to study order-disorder transitions in molecular systems.
结晶除了在技术上具有相关性（例如在化学、食品和制药行业）外，还是物理学和化学的许多方面的基础。然而，由于许多因素会影响结晶过程，因此设计结晶材料和结晶过程通常具有挑战性。作为深入了解分子聚集方式以及分子自身组织成晶体结构的方法的一部分，在这项工作中，我们提出了一种新方法来构建适用于研究分子体系中结晶和多态转变的有序参数。我们的有序参数可以使用晶体简单分子动力学模拟获得的信息为复杂体系系统地定义。我们展示了如何构建三种不同体系的有序参数：溶液中α-甘氨酸晶体的形成、苯从熔体中的结晶以及对苯二甲酸的多态转变。最后，我们提出了如何使用这些有序参数来研究分子体系中的有序-无序转变。
